1. Field of the Invention
The invention relates to a method of and a device for chip-cutting of workpieces, in particular for the cross-cutting and chamfering of extruded plastics material tubes or the like and in which a cutting tool may be fed radially to a rotational displacement of the object relative to the tool.
2. Description of the Prior Art
Methods and devices are already known for the cutting and chamfering of round sections--according to EP-Al No. 0103649--which preferably operate with a revolving cutting system for parting off solid or hollow sections such as extruded plastics material tubes or the like. Upon cutting extruded sections, the cutting system is co-entrained in the direction of extrusion, the section which is to be cut or chamfered being held by gripper elements at either side of the plane of rotation of the tools. Two discs are present in this device, which are driven by two rotors at different rotational speeds. The cutting tools are mounted in radially displaceable manner on the one disc and coupled in motion to the second disc via guiding elements, the guiding elements being located in guiding tracks extending eccentrically to a disc centre. A relative displacement of the two discs is caused by the different rotational speed and the tools are displaced in radial direction by the guiding tracks with respect to the disc bearing the same, in the direction towards the workpiece. The relative displacement of the tools may be interrupted by means of a clutch installed in the transmission line to the disc receiving the guiding tracks. It is possible furthermore to construct the guiding tracks in such a manner that the feed motion of the tools occurs in the manner of an intermittent displacement. The embodiment of a device of this kind requires a special structure of the discs carrying the tools and the control curvatures have no more than a fraction of the circumferential length of a single rotational displacement. The intermittent displacements which may be generated if appropriate by corresponding shaping of the guiding track, are consequently inadequate to prevent the appearance of comparatively long cuttings, which may be wound together, or drawn into the hollow section or caught on the workpiece carriers.
It is also known moreover that the feed drives for tool feed may be acted upon in pulsed manner, or rather in the case of piston/cylinder systems, that these may be displaced by brief pressure surges in mutually opposed directions, to secure tearing-off of the cuttings. These control systems require considerable control complexity and very greatly load the mechanism for transmission of the rotational and feed motions, whereby these are exposed to a high degree of wear.